Steam generator

ABSTRACT

A steam generator of the type used as a component of a pressurized-water power reactor installation, has a preheater to which feed water is supplied via a plenum chamber of extended length connecting with the preheater through a series of holes. The plenum chamber is supplied with feed water via the generator&#39;&#39;s feed-water inlet nozzle which injects a feed-water jet which impinges on an inner wall of the plenum chamber for deflection thereby and flow throughout the plenum chamber. This jet is surrounded by a perforated cylinder through which the deflected feed-water flow must pass for distribution throughout the plenum chamber, the effect being a more uniform distribution of the feed-water flow throughout the plenum chamber and a reduction in the flow resistance which otherwise prevails.

United States Patent 1191 Schriider 1 Nov. 11, 1975 1 1 STEAM GENERATOR [75] inventor: Heinz-.liirgen Schr'ridenErlangen.

Germany [22] Filed: Sept. 12. 1974 [21] Appl. No.: 505.383

[30] Foreign Application Priority Data Primary Eraminer-Kenneth W. Sprague Alrorney. Agent. or FirmKenyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT A steam generator of the type used as u component of n pressurized-water powcr reactor installation. has it preheater to which feed water is supplied via a plenum chamber of extended length connecting with the preheater through a series of holes. The plenum chamber is supplied with feed water via the generators feedwater inlet nozzle which injects a feed-water jet which impinges on an inner wall of the plenum chamber for deflection thereby and flow throughout the plenum chamber. This jet is surrounded by a perforated cylinder through which the deflected feed-water flow must pass for distribution throughout the plenum chamber. the effect being a more uniform distribution of the feed-water flow throughout the plenum chamber and a reduction in the flow resistance which otherwise prevails.

7 Claims. 2 Drawing Figures US. Patent Nov. 11,1975 Sheet 10m 3,918,409

U.S. Patent N0v.1l, 1975 Sheet2of2 3,918,409

STEAM GENERATOR BACKGROUND OF THE INVENTION A pressurized-water reactor i nstalla tion includes a pressure vessel containing a core cooled by a coolant loop whichcirculates pressurized-water through the vessel. This loop includes a circulating pump and a steam generator where the coolant gives up itsheat absorbed from the core. to water which is converted to steam representing useful energy.

The steam generator comprises a vertical housing having its bottom closed by a tube sheet in which the lower ends of a U-shapcd tube bundle are mounted. a primary header below the tube sheet being designed to circulate the coolant through the tube bundle. The top of the housing forms a boiler drum containing water and moisture separators and having a steam outlet noz-" zle for the steam output.

The tube bundle forms inlet and outlet legs. of which the outlet leg is called the cold leg. A cylindrical shroud encloses both legs of the tube bundle and is radially spaced inwardly from the housing to form a descent space through which feed water descends. the bottom of the shroud being spaced above the tube plate so that the descending water can flow inwardly and ascend within the shroud while converting to steam through the heat received from the tube bundle.

A constant supply of feed water is required and in one form of such a steam generator the feed water is supplied through one or more feed-water nozzles in the lower portion of the generator's housing, and to avoid thermal shock. this is commonly done by first passing the feed water from the nozzle to a preheater.

Such a preheater is normally provided by walls inside of the shroud which enclose the lower portion of the cold leg of the tube bundle. the preheater having an outlet to the inside ofthe housing for the preheated feed water. while the feed-water inlet nozzle connects with a plenum chamber which arcuately embraces the outside of the shroud which forms the outer wall ofthe preheater and the inner wall of the plenum chamber. this portion of the shroud having a series of interspaced holes connecting the plenum chamber with the preheater.

The feed-water inlet nozzle introduces the feed water in the form of a jet. the plenum chamber is of substantial arcuate length. and these factors create problems concerning feeding the preheater with uniformly distributed flows of feed water while providing for the minimum possible flow resistance to the feed water which must. of course. be introduced at a pressure which is adequate to force the feed water into the housing where the steam is being generated.

An example oisuch a steam generator is provided by the Webster U.S. Pat. No. 3,766,892. dated Oct. 23. 1973. Here the preheater is formed in two sections and two feed-water inlet nozzles are provided. one for each section. in each instance. the nozzle ejects a jet of feed water towards one of the series of holes through the shroud in a direct fashion. making uniform feeding throughout all oithe series ofholes through the shroud. improbable.

in the Ferraro ct al. U.S. Pat. No. 3.8l L498. dated May 2i. 1974. in one example the arrangement corresponds to that of the Webster patent but the shroud has 2 this Ferraro ct a patent has the shroud openings offset front the feed-water input nozzle so that the incoming jet of feed water strikes a solid portion of the shroud and is directed therefrom for flow throughout the pienum chamber.

In both of the above cases the feed-water input inlet nozzle connects directly with the plenum chamber and it would appear to be a reasonable assumption that this would provide the least possible resistance to the flow of feed water into and throughout the plenum chamber and into the preheater; also. it would appear to be a reasonable assumption that with this apparent low flow resistance there should he a uniform distribution oi feed water through the various openings or perforations in the shroud and. therefore. to the preheater.

SUMMARY OF THE INVENTION The above assumptions are contradicted by the present invention.

According to this invention. the arcuate feed-water plenum chamber extending transversely along the outside ofthe shroud in the space between the shroud and the inside of the generators housing. has the inlet opening. and the feed-water inlet nozzle for the housing has its inner end registered with this inlet opening and connected therewith. the nozzle directing the feedwater jet against the portion of the shroud for deflection therefrom to form defiective flows throughout the plenum chamber and the shroud has the series of inlet holes formed therethrough from the plenum chamber and all of which are offset from the chamber's inlet opening. A perforated plate is positioned directly in the path of the initially deflected feed-water flows. this plate being in the form ofa perforated cylinder extending from the plenum chamber inlet opening almost to the shroud portion which deflects the incoming feedwater jet. Surprisingly. it has been discovered that the initial introduction of the feed water into the plenum chamber via this perforated cylindrical plate effects a more uniform flow ofthefeed water throughout the extent of the plenum chamber and through the holes in the shroud leading to the preheater. while at the same time reducing the overall or total flow resistance to the feed-water overall flow from the feed-water inlet nozzle to the preheaters interior.

These advantages are enhanced by providing the feed-water inlet nozzle internally with a secondary nozzle having a periphery welded to the inside of the outer end of the feed-water inlet nozzle and from which this secondary nozzle converges to a tubular portion having a diameter smaller than that of the feed-water input nozzle and pointing towards the jet impact portion of the shroud. the cylindrical perforated plate being eoncentric with both of these nozzles and the two nozzles being concentric with respect to each other. This secondary nozzle provides a feed-waterjet of increased velocity and. therefore. the shroud portion which receives a multiplicity of perforations instead of the series of openings of the Webster patent; in a second example.

its impact is thickened and has a surface plating of an erosion-resistant metal such as austenitic stainless steel. throughout its impact area.

The cylindrical perforated plate has a substantially larger diameter than the inside diameter ofeither of the two nozzles. the plenum chamber's inlet opening having the same diameter as the cylindrical perforated plate and the latter extends inwardly with an inner end almost. but not quite. touching the plated surface ofthc shroud. This permits relative thermal motion. The picnum chamber's inlet is made to converge from this 3 larger diameter in a direction towards the secondary nozzles inner end to define an opening having the same diameter as that of the inside of the secondary nozzle. these two parts being interspaced to permit thermal movement and the outer end ofthis converging plenum chamber inlet opening being sealed by an elastic metal bellows which extends around the outside and is protected by the tubular portion of the secondary nozzle. this bellows having an outer end fixed via a flaring conical sleeve to the inside of the housings feed-water inlet nozzle adjacent to the secondary nozzles peripheral connection with this inside.

Of course. all of the parts mentioned are made of metal and where connections are required. they are cffected by welding.

BRIEF DESCRIPTION OF THE DRAWINGS The presently preferred mode for carrying out the invention is illustrated by the accompanying drawings, in which:

FIG. I is a vertical section showing the type of steam generator to which the invention is applicable; and

FIG. 2, showing in vertical section and on a relatively much larger scale. the details of the invention itself.

DETAILED DESCRIPTION OF THE INVENTION The steam generator shown by FIG. I is a typical pressurized-water reactor steam generator. It has a vertical cylindrical housing 1 in which the U-shaped tube bundle 2 is enclosed by the shroud 3, the bundles hot leg 4 and cold leg 5 having their bottom ends fixed in a tube plate 6 which closes the bottom of the housing I. The hemispherical primary header is shown at 7 with its interior subdivided by a partition 8 into an inlet manifold 9 and an outlet manifold 10 for feeding the inlet or hot leg 4 and the outlet or cold leg 5 with the pressurized-water reactor coolant circulating from in the coolant loop of a pressurized-water reactor (not shown). This header has the usual inlet and outlet stubs I2 and 13 for the manifolds 9 and 10, respectively.

The upper portion of the housing 1 is enlarged to form the usual boiler drum in containing the water separators 15 mounted on top of the shroud 3 and moisture separators I6 through which the steam exhausts. leaving the boiler drum la via a steam output nozzle 17. The separated water from the separators [5 falls down the annular descent space formed between the radially interspaced housing I and shroud 3. the bottom of the shroud being spaced above the tube sheet 6 so that the descending water flows radially over the tube sheet 6 for upward flow inside the shroud and conversion to the steam.

The feed-water preheater is generally indicated at 21. it being formed by the shroud itself and by the usual walls which form an enclosure around the lower portion of the tube bundles cold leg 5 adjacent to the tube plate 6, with partitions or bafflcs internally providing for the sinuous flows through the tube bundles tubes. In this instance. the preheater 2! comprises an upper section 23 where the feed-water flow 22 is upward and a lower section where the feed-water flow 24 is downward. this lower section being shown at 25. Both sections have outlets for the preheated water flows into feed-water already in the housing. The feed-water inlet nozzle 26 connects with the plenum chamber 26a of the section 21, and a feed-water inlet nozzle 27 connects with the section via that section's plenum chamber 270.

- here the nozzle 26 is shown with its inlet end pointing towards the solid shroud portion 3 to direct a jet of fecd-watcr thereagainst. the thus deflected radial feedwater flow then flowing through the perforations 29 in I the cylindrical plate 30. This perforated cylinder 30 has its outer end welded at 30a to the outer wall 31 of the plenum chamber which extends transversely in a horizontal direction areuately around the shroud portion 3 containing the series of feed holes 26a. this welded connection being via the outwardly tapering chamber inlet connection 33 having an inner larger end matching the diameter of the cylinder 30, itself being welded at 33a to the chamber 31. The outer smaller end of this part 33 is sealed via the elastically flexible metal bellows 34 and its extension 35 which is welded at 36 to the inside of the nozzle 26 adjacent to the latters outer end. This permits thermal movement of the parts. the inner end of the perforated cylinder 30 being spaced from the shroud 3 just enough to accommodate such movement. The part 35 is conical and together with an annular part 35a forms a part of the bellows 34 which is necessarily made of sheet metal, the part 350 being welded to the part 33 at 330.

The secondary nozzle of substantially smaller diameter than the inside diameter of the nozzle 26 is shown with its tubular portion 28 which separates and protects the bellows 34 from the incoming feed water. and having the converging portion 38a which is peripherally welded at 39 to the inside ofthe housings nozzle 26 adjacent to the latters outer end. The inside diameters of the secondary nozzles tubular portion 38 and the annular bellows mounting part 35a are the same.

The previously referred to thickening of the shroud 3 is shown at 40 as comprising a section welded into the shroud with the welds shown at 40a. The plating is shown at 4| and this may be a plating of austcnitic steel having a good resistance to the erosive effect of the high velocity jet of feed water jetted from the secondary nozzles tubular portion 38 directly against the thickened portion 40 which. of course, provides increased mechanical strength for the shroud 3.

In operation. the inlet nozzle 26. which may be the usual feed-water inlet nozzle of the steam generator housing, receives the feed water under the necessary high pressure. The flow is constricted by the converging portion 38a of the secondary nozzle and is smoothed out in this nozzles cylindrical portion 38 and ejected against the plating M from which it is deflected radially outwardly and forced to travel through the perforations 29 of the cylinder 30. This cylinder has a diameter rather substantially greater than the inside diameter of the cylinder 38 of the secondary nozzle. The interior of the cylinder 30 is entirely separated from the water in the generators housing. by the conical chamber inlet 33 and the sealing action of the bellows 34.

As previously noted, the interpositioning of this perforated cylindrical plate 30 has the surprising effect that instead of increasing the overall flow resistance throughout the plenum chamber and preheater as a system. there is a reduction in this overall flow resistance while. at the same time. a much more uniform distribution'is effected throughout the plenum chamber and through the various holes 26u opening into the preheater section 23. I

As previously noted. the internal diameter of the cylindcr 30 is substantially greater than the internal diameter of the tubular part of the secondary nozzle. The holes 29 have a diameter approximately equal to the wall thickness of the cylinder plate 30. while the spacing between the hole centers is substantially twice as large. The diameter of the cylinder 30 is more than fifteen times that of the hole diameter. and about twice the inside diameter of the tube section 38 of the secondary nozzle. These relative dimensions may be varied such as in the order of 30% one way or the other.

What is claimed is:

l. A steam generator comprising a housing. a tube plate closing the bottom of said housing. a tube bundle mounted in said tube plate. a shroud surrounding at least a portion of said tube bundle adjacent to said tube plate and spaced inwardly from said housing. a space being formed between said shroud and said housing. walls inside of said shroud and with the latter forming a feed-water preheater having an outlet to said housing. a feed-water plenum chamber extending transversely along the outside of said shroud in said space and having an inlet opening. and a feed-water inlet nozzle for said housing and having an inner end registered with and connected with said inlet opening. said nozzle directing a feed-waterjet against a portion of said shroud for deflection thereby to form deflected flows throughout said plenum chamber and said shroud having a se- 6 ries of inlet holes formed thercthrough from said plenum chamber and all of which are offset from the chambcrs said inlet opening; wherein the improvement comprises a perforated plate positioned in the paths of said deflected flows.

2. The generator of claim 1 in which said plate is cylindrical and extends from the chambcrs said inlet substantially to said shroud.

3. The generator of claim 2 in which a second nozzle has an outer end fixed to the outer inside end of the aforesaid nozzle and converges therefrom to form a tube spaced inwardly from the aforesaid nozzle and having an inner end pointing towards and spaced from said shroud. I

4. The generator of claim 3 in which the portion of said shroud against which said jet is directed. is covered by an erosion-resistant plating.

5. The generator of claim 3 in which the portion of said shroud against which said jet is directed. is increased in thickness.

6. The generator of claim 3 in which the plenum chambers said inlet converges to an outer end adjacent to said inner end of said second nozzle and forms an entrance of substantially the same cross-sectional area and shape as those of the second nozzles said inner end.

7. The generator of claim 6 in which a bellows encircles said second nozzle inside the first-named nozzle andhas an outer end fixed to the inside of this firstnamed nozzle and an inner end fixed to said outer end of the plenum chambers said inlet.

t i t i t Patent No. 3,918,409 Dated November 11, 1975 Q Inventor) Heinz-Jurgen Schrdder Pa 1 f 3 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Q Insert the attched sheets of drawings, as part of Letters Patent 3,918,409.

Signed and Sealed this Twenty-seventh Day Of July 1976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'larenls and Trademarks Us. Patent Nov.11,1975 SheetlofZ 3,918,409

I Pag 2 of 3 

1. A steam generator comprising a housing, a tube plate closing the bottom of said housing, a tube bundle mounted in said tube plate, a shroud surrounding at least a portion of said tube bundle adjacent to said tube plate and spaced inwardly from said housing, a space being formed between said shroud and said housing, walls inside of said shroud and with the latter forming a feed-water preheater having an outlet to said housing, a feedwater plenum chamber extending transversely along the outside of said shroud in said space and having an inlet opening, and a feed-water inlet nozzle for said housing and having an inner end registered with and connected with said inlet opening, said nozzle directing a feed-water jet against a portion of said shroud for deflection thereby to form deflected flows throughout said plenum chamber and said shroud having a series of inlet holes formed therethrough from said plenum chamber and all of which are offset from the chamber''s said inlet opening; wherein the improvement comprises a perforated plate positioned in the paths of said deflected flows.
 2. The generator of claim 1 in which said plate is cylindrical and extends from the chamber''s said inlet substantially to said shroud.
 3. The generator of claim 2 in which a second nozzle has an outer end fixed to the outer inside end of the aforesaid nozzle and converges therefrom to form a tube spaced inwardly from the aforesaid nozzle and having an inner end pointing towards and spaced from said shroud.
 4. The generator of claim 3 in which the portion of said shroud against which said jet is directed, is covered by an erosion-resistant plating.
 5. The generator of claim 3 in which the portion of said shroud against which said jet is directed, is increased in thickness.
 6. The generator of claim 3 in which the plenum chamber''s said inlet converges to an outer end adjacent to said inner end of said second nozzle and forms an entrance of substantially the same cross-sectional area and shape as those of the second nozzle''s said inner end.
 7. The generator of claim 6 in which a bellows encircles said second nozzle inside the first-named nozzle and has an outer end fixed to the inside of this first-named nozzle and an inner end fixed to said outer end of the plenum chamber''s said inlet. 